Your back issues would be the biggest concern...JMO. Even in just light duty no real heavy grunt work - just running power equipment would be an issue or potential issue. I'd avoid serious back issues like the plague or work that would aggravate it. If I was looking for helper I would not hire you. Not trying to be jerk but I would only hire fit and trim athletic type folks for all aspects of my business. I'm 45 myself and I can easily pass for mid 30's and I'm in very good shape for my age not much worse for the wear [hernia is the only exception] over what I was when I was 27 or so. Taking a financial gamble less of an issue - it's just money.
In this industry there are many half price hacks - even the mowing rates in my area from established reputable companies are low. If I would of kept a $35 min charge for mowing tiny lawns and taken the advice of many posters here 3+ years ago on lawnsite "bid like you don't need them" I would of been out of business already. There will always be those here that say their customers will fall all over themselves to cut a you $45 check for a tiny lawn that only took them 12 min to mow and trim. Besides many people don't like riding mowers on their property. Frankly if I was to ever retire someday and I hired a lawn Co. I'd rather not see someone riding around on a ZTR who looks like they needs to be walking behind a lighter mower for the exercise benefit alone. Even out of shape, overweight, age challenged, homely customers prefer to look at healthy, high energy, fit and able bodied toned workers on their property. It's a cruel world but it is what it is.
I think pizza delivery is good option for extra $....frankly may do that myself this winter instead of snow again. All the best